The present research program will receive the offspring of adult female monkeys which have been exposed in other research projects to 0.5-5 ppm of polychlorinated biphenyls (PCBs) in their daily diet prior to and throughout pregnancy and for four months of nursing of the offspring, but will not be involved in exposing any subjects to PCBs. the present project will then maintain these offspring on normal diets and will periodically monitor them for clinical health and body burdens of PCBs. These offspring will be subjected to a broad battery of behavioral tests to assess behavioral toxicology possibly resulting from the fetal and neonatal exposure to PCBs. Offspring will be available from monkeys fed either Aroclor 1248, or Aroclor 1016, or PCB residues derived from contaminated great lakes fish, allowing a comparison of the relative toxicities of these three PCB mixtures. From graphs of quantitative behavioral measures plotted against PCB body burdens, it is planned to determine whether there appears to exist a threshold of PCB dosage or of PCB body burdens below which toxic effects are not seen. If so, then the data should permit quantitative estimates of this threshold limit body burden. The data will permit a comparison of threshold limits derived both from clinical health assessments and from behavioral tests. Comparison of adult exposed and fetal-neonatal exposed monkeys will assess whether the developing organism is more vulnerable than the adult to toxic damage from PCBs. Emphasis will be on the detection of irreversible effects of PCB exposures through testing of the animals over several years following exposure.